Gelatins in the form of heat-denatured collagens are widely employed as gelling agents, foaming agents, thickeners, and the like in foods, cosmetics, and the like. They are also employed for drug capsules. Collagens are fibrous proteins that, together with elastins, constitute animal connective tissue. Their applications include foods, cosmetics, pharmaceuticals, paints, and plastic materials.
Gelatins and collagens generally have molecular weights of roughly 100,000 to 300,000. Digested gelatins and collagens generally have molecular weights of not greater than 10,000.
However, given the various and sundry applications listed above, there is a need for collagens and gelatins having desirable properties such as low antigenicity, high solubility, low gelling strength, the ability to readily form films, and the ability to readily clathrate other molecules. Thus, there is demand for gelatins and collagens with molecular weights other than those stated above.
In the past, proteases and collagenases have been employed to degrade gelatins and collagens to achieve lower molecular weights. It is known that these enzymes can be obtained by cultivating Achromobacter iophagus and Clostridium histolyticum. 
However, there are problems in that these microbes have been determined to be pathogenic and must be cultured under anaerobic conditions. Achieving large quantities of enzyme from these microbes involves complex operations. Further, the enzymes obtained from these microbes end up degrading gelatins and collagens into minimal units (molecular weights of several hundred to several thousand), precluding the obtaining of gelatin and collagen degradation products of suitable molecular weight.
Collagenase from the small intestine is also known. This enzyme is expensive. Obtaining it entails a complex operation, and achieving large-volume production is difficult. Thus, the use of this substance cannot be considered industrially advantageous. Further, this collagenase degrades collagen into a molecular weight of several hundred to several thousand.
Accordingly, the present inventors first conducted extensive investigation with the goal of providing an enzyme for manufacturing degradation products of gelatins and collagens of suitable molecular weight. As the result of extensive exploration of the natural world for enzymes degrading gelatins and collagens into peptides of suitable molecular weight, they discovered in soil a microbe producing an enzyme degrading gelatins and collagens with molecular weights of about 130,000 into peptides with molecular weights of about 70,000 and about 40,000 and submitted a patent application (Japanese Patent Application Publication No. 2000-102381).
The protease described in the above-cited patent application publication comprises the following five properties:
(1) Function
The protease exhibits limited degradation activity by degrading heat-denatured collagens with a molecular weight of about 130,000 and nondenatured soluble collagens of about 300,000 in molecular weight into peptides of about 70,000 and 40,000 in molecular weight, but exhibits only slight degradation activity on the synthetic substrate DNP-Pro-Gln-Gly-Ile-Ala-Gly-Gln-D-Arg, a collagenase substrate, and no degradation activity on the synthetic substrate DNP-Gln-Gly-Ile-Ala-Gly-Gln-D-Arg. Further, it exhibits degradation activity on azocol or casein. Here, DNP denotes a dinitrophenyl group and D denotes the D form of Arg.
(2) Optimal pH:
pH 5.5 to 7
(3) Optimal Temperature:
37 to 40° C.
(4) Molecular Weight
23,000±2,000 (by SDS-PAGE)
(5) Enzyme Inhibition:
Activity is inhibited by o-phenanthroline and L-cysteine, but not by ethylenediamine tetraacetic acid, N-ethylmaleimide, phenylmethanesulfonyl fluoride, or iodoacetamide.
The above protease is manufactured by culturing a protease-producing bacterium of the genus Microbacterium and extracting the protease from the culture product. In the above-cited patent application publication, it is disclosed that the above protease is manufactured by culturing a protease-producing bacterium of the genus Aureobacterium and extracting the protease from the culture product. However, upon subsequent examination, we have lumped the genus Aureobacterium with the genus Microbacterium. 
As the result of further research, the present inventors discovered that the above culture contained a new protease in addition to the above-stated protease, that this protease had cleavage specificity for a different amino acid sequence than the protease in the above-cited patent application publication, and that it was an enzyme capable of decomposing gelatin and collagen into large fragments. The present invention was devised by determining the amino acid sequence and base sequence corresponding to this enzyme.